Compensatory Head Movements Research Articles

Vertical pelvic movement asymmetry and lameness location in ipsilateral combined forelimb and hindlimb lameness cases.

Compensatory vertical head and pelvis movement asymmetry may occur in trotting horses with a primary cause of lameness in one end of the body due to the weight shifting between limbs, leading to apparent combined forelimb and hindlimb lameness (CFHL). Little is known about CFHL patterns observed with body-mounted inertial sensors (BMIS) and regardless of their underlying mechanisms, compensatory and secondary lameness may complicate the definitive identification of the primary causes of lameness. Determine associations between vertical pelvic movement asymmetry and location of primary lameness in ipsilateral CFHL cases where hindlimb lameness is solely impact or push-off type. Retrospective cohort. From a body-mounted inertial sensor (BMIS) evaluated equine lameness database, we identified cases with a consistent, low-variability ipsilateral impact (IpI) or ipsilateral pushoff (IpP) hindlimb lameness in a straight-line trot and that had definitive diagnoses. Cases were categorised by lameness location to the limb(s), diagnosis, and ratio of the amplitude of forelimb to hindlimb lameness (Forea/Hinda). Differences in the numbers of IpI and IpP cases in these categories were analysed with chi-square tests, effect sizes, and odds ratios. Among the 2375 total lameness cases screened, 49 IpI and 36 IpP cases met the criteria for consistency, low variability, and definitive diagnosis. IpI cases were more likely than IpP cases to have forelimb-only lameness causes when Forea/Hinda >1 (OR = 43, 95% CI = 2.3-798). IpP cases were more likely than IpI cases to have hindlimb-only causes at both Forea/Hinda >1.0 (OR = 20, 95% CI = 2.2-200) and <1.0 (OR = 14, 95% CI = 2.9-66.7). Compared with IpI, IpP cases were more frequently diagnosed with tendon, suspensory ligament, or high-motion joint disorders in hindlimbs (OR = 3.6, 95% CI = 1.1-12.3) and less with unknown causes (OR = 13.2, 95% CI = 3.2-75.2). In IpI cases, positive forelimb regional anaesthesia often reduced hindlimb lameness, whereas in IpP cases, positive hindlimb regional anaesthesia typically lessened forelimb lameness. Most cases were Quarter Horses. The likelihood of location and cause of lameness may be different for other breeds. The type of pelvic movement asymmetry observed in IpI and IpP cases is linked to the location and underlying cause of the primary lameness.

WatchCap: Improving Scanning Efficiency in People with Low Vision through Compensatory Head Movement Stimulation

Individuals with low vision (LV) frequently face challenges in scanning performance, which in turn complicates daily activities requiring visual recognition. Although those with PVL can theoretically compensate for these scanning deficiencies through the use of active head movements, few practical applications have sought to capitalize on this potential, especially during visual recognition tasks. In this paper, we present WatchCap, a novel device that leverages the hanger reflex phenomenon to naturally elicit head movements through stimulation feedback. Our user studies, conducted with both sighted individuals in a simulated environment and people with glaucoma-related PVL, demonstrated that WatchCap's scanning-contingent stimulation enhances visual exploration. This improvement is evidenced by the fixation and saccade-related features and positive feedback from participants, which did not cause discomfort to the users. This study highlights the promise of facilitating head movements to aid those with LVs in visual recognition tasks. Critically, since WatchCap functions independently of predefined or task-specific cues, it has a wide scope of applicability, even in ambient task situations. This independence positions WatchCap to complement existing tools aimed at detailed visual information acquisition, allowing integration with existing tools and facilitating a comprehensive approach to assisting individuals with LV.

The motor apparatus of head movements in the Oleander hawkmoth (Daphnis nerii, Lepidoptera).

Head movements of insects play a vital role in diverse locomotory behaviors including flying and walking. Because insect eyes move minimally within their sockets, their head movements are essential to reduce visual blur and maintain a stable gaze. As in most vertebrates, gaze stabilization behavior in insects requires the integration of both visual and mechanosensory feedback by the neck motor neurons. Although visual feedback is derived from the optic flow over the retina of their compound eyes, mechanosensory feedback is derived from their organs of balance, similar to the vestibular system in vertebrates. In Diptera, vestibular feedback is derived from the halteres-modified hindwings that evolved into mechanosensory organs-and is integrated with visual feedback to actuate compensatory head movements. However, non-Dipteran insects, including Lepidoptera, lack halteres. In these insects, vestibular feedback is obtained from the antennal Johnston's organs but it is not well-understood how it integrates with visual feedback during head movements. Indeed, although head movements are well-studied in flies, the underlying motor apparatus in non-Dipteran taxa has received relatively less attention. As a first step toward understanding compensatory head movements in the Oleander hawkmoth Daphnis nerii, we image the anatomy and architecture of their neck joint sclerites and muscles using X-ray microtomography, and the associated motor neurons using fluorescent dye fills and confocal microscopy. Based on these morphological data, we propose testable hypotheses about the putative function of specific neck muscles during head movements, which can shed light on their role in neck movements and gaze stabilization.

Prosthetic Stimulation of the Vestibular Nerve Can Evoke Robust Eye and Head Movements Despite Prior Labyrinthectomy.

Prosthetic electrical stimulation can evoke compensatory eye and head movement despite vestibular implant electrode insertion occurring years after prior labyrinthectomy. Vestibular implants sense head rotation and directly stimulate the vestibular nerve, bypassing damaged end organs. Animal research and current clinical trials have demonstrated the efficacy of this approach. However, candidacy criteria for vestibular implants currently require presence of a patent labyrinth in the candidate ear and at least aidable hearing in the opposite ear, thus excluding patients who have undergone prior labyrinthectomy for unilateral Menière's disease that later progressed to bilateral vestibular hypofunction. Eight years after right unilateral labyrinthectomy, we implanted stimulating electrodes in the previously exenterated right ear ampullae of a rhesus macaque monkey. The left labyrinth had long-standing hypofunction due to intratympanic gentamicin injection and surgical disruption. We used three-dimensional video-oculography to measure eye movement responses to prosthetic electrical stimulation. We also measured head-movement responses to prosthetic stimulation with the head unrestrained. Bilateral vestibular hypofunction was confirmed by absence of vestibuloocular reflex responses to whole-body rotation without prosthetic stimulation. For a subset of the implanted electrodes, prosthetic vestibular stimulation evoked robust compensatory eye and head movements. One electrode reliably elicited responses aligned with the implanted ear's anterior canal nerve regardless of the return electrode used. Similarly, a second electrode also elicited responses consistent with excitation of the horizontal canal nerve. Responses grew quasilinearly with stimulation rate and current amplitude. Prosthetic electrical stimulation targeting the vestibular nerve can be effective years after labyrinthectomy, if at least some parts of the vestibular nerve's ampullary branches remain despite destruction or removal of the membranous labyrinth.

Automatic measurement of mouse visual acuity based on optomotor response: SKY optomotry.

In the field of visual science study using rodents, several assessment methods have been developed for measuring visual function. However, methods such as electroretinograms tests, visual evoked potentials tests and maze tests have limitations in that they measure function of only a specific type of cells, are difficult to quantify or require sufficient training time. The method which uses an optokinetic reflex and optomotor response, a compensatory eye and head movement in response to changes in the visual scene, became the most widely used method. However, this method requires highly trained experimenters and is time consuming. We showed that measured visual acuity values are significantly different between beginner and expert. Here we suggest an automated optometry program, 'SKY optomotry', which automatically tracks rodents' optomotor response to overcome subjectivity and the lengthy scoring procedure of the existing method. To evaluate the performance of SKY optomotry using 8-12-week-old C57BL/6 mice we compared the binomial decision of SKY optomotry with a skilled expert, and the area under the curve of SKY optomotry was 0.845. Comparing the final visual acuity, the intraclass correlation coefficient value between SKY optomotry and an expert was 0.860 (95% confidence interval (CI) 0.709-0.928), whereas that between an expert and a beginner was 0.642 (95% CI 0.292-0.811). SKY optomotry showed an excellent level of performance with good inter-rater agreements based on the visual acuity measured by an expert. With the use of our application, researchers will be able to test an experimental animal's eyesight more accurately while saving time on specialized training.

Integration of visual and antennal mechanosensory feedback during head stabilization in hawkmoths.

During flight maneuvers, insects exhibit compensatory head movements which are essential for stabilizing the visual field on their retina, reducing motion blur, and supporting visual self-motion estimation. In Diptera, such head movements are mediated via visual feedback from their compound eyes that detect retinal slip, as well as rapid mechanosensory feedback from their halteres - the modified hindwings that sense the angular rates of body rotations. Because non-Dipteran insects lack halteres, it is not known if mechanosensory feedback about body rotations plays any role in their head stabilization response. Diverse non-Dipteran insects are known to rely on visual and antennal mechanosensory feedback for flight control. In hawkmoths, for instance, reduction of antennal mechanosensory feedback severely compromises their ability to control flight. Similarly, when the head movements of freely flying moths are restricted, their flight ability is also severely impaired. The role of compensatory head movements as well as multimodal feedback in insect flight raises an interesting question: in insects that lack halteres, what sensory cues are required for head stabilization? Here, we show that in the nocturnal hawkmoth Daphnis nerii, compensatory head movements are mediated by combined visual and antennal mechanosensory feedback. We subjected tethered moths to open-loop body roll rotations under different lighting conditions, and measured their ability to maintain head angle in the presence or absence of antennal mechanosensory feedback. Our study suggests that head stabilization in moths is mediated primarily by visual feedback during roll movements at lower frequencies, whereas antennal mechanosensory feedback is required when roll occurs at higher frequency. These findings are consistent with the hypothesis that control of head angle results from a multimodal feedback loop that integrates both visual and antennal mechanosensory feedback, albeit at different latencies. At adequate light levels, visual feedback is sufficient for head stabilization primarily at low frequencies of body roll. However, under dark conditions, antennal mechanosensory feedback is essential for the control of head movements at high frequencies of body roll.

Effects of driver compensatory behaviour on risks of critical pedestrian collisions under simulated visual field defects.

Compensatory behaviour is regarded as a helpful strategy to mediate drivers’ deteriorated hazard perception ability due to visual field defects. However, helpfulness of compensatory behaviour for drivers with advanced visual field defects has largely unexplored. This study aims to clarify the effectiveness and limitation of compensatory head movements in critical situations where included pedestrians stepping off a sidewalk under the simulation of advanced visual defects. 18 healthy-sighted drivers participated the data collection that was conducted in a driving simulator under three driving conditions: (1) without visual impairment, (2) with visual impairment and not performing active compensation, and (3) with visual impairment but performing active compensation. The result showed that active compensation led quick accelerator and brake response times, reducing the risk and number of pedestrian collisions. The active compensation led a decrease in the number of non-responses to hazardous pedestrians compared to while driving not performing compensation. However, the compensation could not reduce the number of pedestrian collisions to those of healthy-sighted drivers. Compensatory viewing behaviour contributed to improved driving performance as well as has limits to lead driving performance like healthy-sighted drivers. Developing driver assistance systems and practical compensatory strategies concerning the degrees of impairment and traffic conditions may provide opportunities to improve driving safety deteriorated hazard perception for visually impaired drivers.

Using Optical Coherence Tomography and Optokinetic Response As Structural and Functional Visual System Readouts in Mice and Rats.

Optical coherence tomography (OCT) is a fast, non-invasive, interferometric technique allowing high-resolution retinal imaging. It is an ideal tool for the investigation of processes of neurodegeneration, neuroprotection and neuro-repair involving the visual system, as these often correlate well with retinal changes. As a functional readout, visually evoked compensatory eye and head movements are commonly used in experimental models involving the visual function. Combining both techniques allows a quantitative in vivo investigation of structure and function, which can be used to investigate the pathological conditions or to evaluate the potential of novel therapeutics. A great benefit of the presented techniques is the possibility to perform longitudinal analyses allowing the investigation of dynamic processes, reducing variability and cuts down the number of animals needed for the experiments. The protocol described aims to provide a manual for acquisition and analysis of high quality retinal scans of mice and rats using a low cost customized holder with an option to deliver inhalational anesthesia. Additionally, the proposed guide is intended as an instructional manual for researchers using optokinetic response (OKR) analysis in rodents, which can be adapted to their specific needs and interests.

Vertical movement symmetry of the withers in horses with induced forelimb and hindlimb lameness at trot.

SummaryBackgroundThe main criteria for lameness assessment in horses are head movement for forelimb lameness and pelvic movement for hindlimb lameness. However, compensatory head nod in horses with primary hindlimb lameness is a well‐known phenomenon. This compensatory head nod movement can be easily misinterpreted as a sign of primary ipsilateral forelimb lameness. Therefore, discriminating compensatory asymmetries from primary directly pain‐related movement asymmetries is a prerequisite for successful lameness assessment.ObjectivesTo investigate the association between head, withers and pelvis movement asymmetry in horses with induced forelimb and hindlimb lameness.Study designExperimental study.MethodsIn 10 clinically sound Warmblood riding horses, forelimb and hindlimb lameness were induced using a sole pressure model. The horses were then trotted on a treadmill. Three‐dimensional optical motion capture was used to collect kinematic data from reflective markers attached to the poll, withers and tubera sacrale. The magnitude and side (left or right) of the following symmetry parameters, vertical difference in minimum position, maximum position and range‐up were calculated for head, withers, and pelvis. Mixed models were used to analyse data from induced forelimb and hindlimb lameness.ResultsFor each mm increase in pelvic asymmetry in response to hindlimb lameness induction, withers movement asymmetry increased by 0.35–0.55 mm, but towards the contralateral side. In induced forelimb lameness, for each mm increase in head movement asymmetry, withers movement asymmetry increased by 0.05–0.10 mm, in agreement with the head movement asymmetry direction, both indicating lameness in the induced forelimb.Main limitationsResults must be confirmed in clinically lame horses trotting overground.ConclusionsThe vertical asymmetry pattern of the withers discriminated a head nod associated with true forelimb lameness from the compensatory head movement asymmetry caused by primary hindlimb lameness. Measuring movement symmetry of the withers may, thus, aid in determining primary lameness location.

A gyroscopic advantage: phylogenetic patterns of compensatory movements in frogs

Head and eye compensatory movements known as vestibulo-ocular and vestibulo-cervical reflexes are essential to stay orientated in space while moving. We have used a previously developed methodology focused on the detailed mathematical description of head compensatory movements in frogs without the need for any surgical procedures on the examined specimens. Our comparative study comprising 35 species of frogs from different phylogenetic backgrounds revealed species-specific head compensatory abilities ensuring gaze stabilization. Moreover, we found a strong phylogenetic signal highlighting the great ability of compensatory head movements in families of Pyxicephalidae and Rhacophoridae from the Natatanura group. By contrast, families of Dendrobatidae and Microhylidae exhibited only poor or no head compensatory movements. Contrary to our expectation, the results did not corroborate an ecomorphological hypothesis anticipating a close relationship between ecological parameters and the head compensatory movements. We did not find any positive association between more complex (3D structured, arboreal or aquatic) habitats or more saltatory behavior and elevated abilities of head compensatory movements. Moreover, we found compensatory movements in most basal Archeobatrachia, giving an indication of common ancestry of these abilities in frogs that are variously pronounced in particular families. We hypothesize that the uncovered proper gaze stabilization during locomotion provided by the higher head compensatory abilities can improve or even enable visual perception of the prey. We interpret this completely novel finding as a possible gyroscopic advantage in a foraging context. We discuss putative consequences of such advanced neuromotor skills for diversification and ecological success of the Natatanura group.

Head movements quadruple the range of speeds encoded by the insect motion vision system in hawkmoths.

Flying insects use compensatory head movements to stabilize gaze. Like other optokinetic responses, these movements can reduce image displacement, motion and misalignment, and simplify the optic flow field. Because gaze is imperfectly stabilized in insects, we hypothesized that compensatory head movements serve to extend the range of velocities of self-motion that the visual system encodes. We tested this by measuring head movements in hawkmoths Hyles lineata responding to full-field visual stimuli of differing oscillation amplitudes, oscillation frequencies and spatial frequencies. We used frequency-domain system identification techniques to characterize the head's roll response, and simulated how this would have affected the output of the motion vision system, modelled as a computational array of Reichardt detectors. The moths' head movements were modulated to allow encoding of both fast and slow self-motion, effectively quadrupling the working range of the visual system for flight control. By using its own output to drive compensatory head movements, the motion vision system thereby works as an adaptive sensor, which will be especially beneficial in nocturnal species with inherently slow vision. Studies of the ecology of motion vision must therefore consider the tuning of motion-sensitive interneurons in the context of the closed-loop systems in which they function.

Head, withers and pelvic movement asymmetry and their relative timing in trot in racing Thoroughbreds in training.

SummaryBackgroundHorses show compensatory head movement in hindlimb lameness and compensatory pelvis movement in forelimb lameness but little is known about the relationship of withers movement symmetry with head and pelvic asymmetry in horses with naturally occurring gait asymmetries.ObjectivesTo document head, withers and pelvic movement asymmetry and timing differences in horses with naturally occurring gait asymmetries.Study designRetrospective analysis of gait data.MethodsHead, withers and pelvic movement asymmetry and timing of displacement minima and maxima were quantified from inertial sensors in 163 Thoroughbreds during trot‐ups on hard ground. Horses were divided into 4 subgroups using the direction of head and withers movement asymmetry. Scatter plots of head vs. pelvic movement asymmetry illustrated how the head–withers relationship distinguishes between contralateral and ipsilateral head–pelvic movement asymmetry. Independent t test or Mann–Whitney U test (P<0.05) compared pelvic movement asymmetry and timing differences between groups.ResultsThe relationship between head and withers asymmetry (i.e. same sided or opposite sided asymmetry) predicts the relationship between head and pelvic asymmetry in 69–77% of horses. Pelvic movement symmetry was significantly different between horses with same sign vs. opposite sign of head–withers asymmetry (P<0.0001). Timing of the maximum head height reached after contralateral (‘sound’) stance was delayed compared to withers (P = 0.02) and pelvis (P = 0.04) in horses with contralateral head–withers asymmetry.Main limitationsThe clinical lameness status of the horses was not investigated.ConclusionIn the Thoroughbreds with natural gait asymmetries investigated here, the direction of head vs. withers movement asymmetry identifies the majority of horses with ipsilateral and contralateral head and pelvic movement asymmetries. Withers movement should be further investigated for differentiating between forelimb and hindlimb lame horses. Horses with opposite sided head and withers asymmetry significantly delay the upward movement of the head after ‘sound’ forelimb stance.

Comparison of optomotor and optokinetic reflexes in mice

During animal locomotion or position adjustments, the visual system uses image stabilization reflexes to compensate for global shifts in the visual scene. These reflexes elicit compensatory head movements (optomotor response, OMR) in unrestrained animals or compensatory eye movements (optokinetic response, OKR) in head-fixed or unrestrained animals exposed to globally rotating striped patterns. In mice, OMR are relatively easy to observe and find broad use in the rapid evaluation of visual function. OKR determinations are more involved experimentally but yield more stereotypical, easily quantifiable results. The relative contributions of head and eye movements to image stabilization in mice have not been investigated. We are using newly developed software and apparatus to accurately quantitate mouse head movements during OMR, quantitate eye movements during OKR, and determine eye movements in freely behaving mice. We provide the first direct comparison of OMR and OKR gains (head or eye velocity/stimulus velocity) and find that the two reflexes have comparable dependencies on stimulus luminance, contrast, spatial frequency, and velocity. OMR and OKR are similarly affected in genetically modified mice with defects in retinal ganglion cells (RGC) compared with wild-type, suggesting they are driven by the same sensory input (RGC type). OKR eye movements have much higher gains than the OMR head movements, but neither can fully compensate global visual shifts. However, combined eye and head movements can be detected in unrestrained mice performing OMR, suggesting they can cooperate to achieve image stabilization, as previously described for other species.NEW & NOTEWORTHY We provide the first quantitation of head gain during optomotor response in mice and show that optomotor and optokinetic responses have similar psychometric curves. Head gains are far smaller than eye gains. Unrestrained mice combine head and eye movements to respond to visual stimuli, and both monocular and binocular fields are used during optokinetic responses. Mouse OMR and OKR movements are heterogeneous under optimal and suboptimal stimulation and are affected in mice lacking ON direction-selective retinal ganglion cells.

A system to measure the Optokinetic and Optomotor response in mice

BackgroundVisually evoked compensatory head movements (Optomotor responses) or eye movements (Optokinetic responses) are extensively used in experimental mouse models for developmental defects, pathological conditions, and testing the efficacy of therapeutic manipulations. New methodWe present an automated system to measure Optomotor and Optokinetic responses under identical stimulation conditions, enabling a direct comparison of the two reflexes. A semi-automated calibration procedure and a commercial eye tracker are used to record angular eye velocity in the restrained animal. Novel video tracking algorithms determine the location of the mouse head in real time and allow repositioning of the stimulus relative to the mouse head. ResultsOptomotor and Optokinetic responses yield comparable results with respect to determining visual acuity in mice. Our new head tracking algorithms enable a far more accurate analysis of head angle determination, and reveal individual head retractions, analogous to saccadic eye movements observed during Optokinetic Nystagmus. Comparison with existing methodsTo our knowledge this is the first apparatus allowing the direct comparison of Optomotor and Optokinetic responses in mice. Our tracking algorithms, which allow an objective determination of head movements are a significant increment over existing systems which rely on subjective human observation. The increased accuracy of the novel algorithms increases the robustness of automated Optomotor response determinations and reveals novel aspects of this reflex. ConclusionsWe provide the blueprints for inexpensive hardware, and release open source software for our system, and describe an accurate and accessible method for Optomotor and Optokinetic response determination in mice.

Compensatory eye and head movements of patients with homonymous hemianopia in the naturalistic setting of a driving simulation.

Homonymous hemianopia (HH) is a frequent deficit resulting from lesions to post-chiasmal brain structures with a significant negative impact on activities of daily living. To address the question how patients with HH may compensate their visual field defect in a naturalistic environment, we performed a driving simulation experiment and quantitatively analyzed both eye and head movements using a head-mounted pupil camera. 14 patients with HH and 14 matched healthy control subjects participated in the study. Based on the detection performance of dynamically moving obstacles, which appeared unexpectedly along the sides of the road track, we divided the patient group into a high- and a low-performance group. Then, we compared parameters of eye and head movements between the two patient groups and the matched healthy control group to identify those which mediate successful detection of potentially hazardous objects. Differences in detection rates could not be explained by demographic variables or the extent of the visual field defect. Instead, high performance of patients with HH in the naturalistic setting of our driving simulation depended on an adapted visual exploratory behavior characterized by a relative increase in the amplitude and a corresponding increase in the peak velocity of saccades, widening horizontally the distribution of eye movements, and by a shift of the overall distribution of saccades into the blind hemifield. The result of the group comparison analyses was confirmed by a subsequent stepwise regression analysis which identified the horizontal spread of eye movements as single factor predicting the detection of hazardous objects.

Head movements evoked in alert rhesus monkey by vestibular prosthesis stimulation: implications for postural and gaze stabilization.

The vestibular system detects motion of the head in space and in turn generates reflexes that are vital for our daily activities. The eye movements produced by the vestibulo-ocular reflex (VOR) play an essential role in stabilizing the visual axis (gaze), while vestibulo-spinal reflexes ensure the maintenance of head and body posture. The neuronal pathways from the vestibular periphery to the cervical spinal cord potentially serve a dual role, since they function to stabilize the head relative to inertial space and could thus contribute to gaze (eye-in-head + head-in-space) and posture stabilization. To date, however, the functional significance of vestibular-neck pathways in alert primates remains a matter of debate. Here we used a vestibular prosthesis to 1) quantify vestibularly-driven head movements in primates, and 2) assess whether these evoked head movements make a significant contribution to gaze as well as postural stabilization. We stimulated electrodes implanted in the horizontal semicircular canal of alert rhesus monkeys, and measured the head and eye movements evoked during a 100ms time period for which the contribution of longer latency voluntary inputs to the neck would be minimal. Our results show that prosthetic stimulation evoked significant head movements with latencies consistent with known vestibulo-spinal pathways. Furthermore, while the evoked head movements were substantially smaller than the coincidently evoked eye movements, they made a significant contribution to gaze stabilization, complementing the VOR to ensure that the appropriate gaze response is achieved. We speculate that analogous compensatory head movements will be evoked when implanted prosthetic devices are transitioned to human patients.

Effect of lungeing on head and pelvic movement asymmetry in horses with induced lameness

Lungeing is an important part of lameness examinations, since the circular path enforced during lungeing is thought to accentuate low grade lameness. However, during lungeing the movement of sound horses becomes naturally asymmetric, which may mimic lameness. Also, compensatory movements in the opposite half of the body may mimic lameness. The aim of this study was to objectively study the presence of circle-dependent and compensatory movement asymmetries in horses with induced lameness. Ten horses were trotted in a straight line and lunged in both directions on a hard surface. Lameness was induced (reversible hoof pressure) in each limb, one at a time, in random order. Vertical head and pelvic movements were measured with body-mounted, uni-axial accelerometers. Differences between maximum and minimum height observed during/after left and right stance phases for the head (HDmax, HDmin) and pelvis (PDmax, PDmin) were measured. Mixed models were constructed to study the effect of lungeing direction and induction, and to quantify secondary compensatory asymmetry mechanisms in the forelimbs and hind limbs. Head and pelvic movement symmetries were affected by lungeing. Minimum pelvic height difference (PDmin) changed markedly, increasing significantly during lungeing, giving the impression of inner hind limb lameness. Primary hind limb lameness induced compensatory head movement, which mimicked an ipsilateral forelimb lameness of almost equal magnitude to the primary hind limb lameness. This could contribute to difficulty in correctly detecting hind limb lameness. Induced forelimb lameness caused both a compensatory contralateral (change in PDmax) and an ipsilateral (change in PDmin) hind limb asymmetry, potentially mimicking hind limb lameness, but of smaller magnitude. Both circle-dependent and compensatory movement mechanisms must be taken into account when evaluating lameness.

Head and body stabilization in blowflies walking on differently structured substrates

Visually guided animals depend heavily on the quality of visual signals in order to obtain functionally relevant information about their environment. To support visual information processing, nature has evolved a large variety of physiological adaptations and behavioral strategies such as compensatory head movements. During self-movement, head rotations compensate for changes in body attitude in order to stabilize gaze. However, how walking animals cope with uneven structured substrates, which may affect body and gaze orientation, is still unknown. We used stereo high-speed video to analyze compensatory head movements of blowflies walking freely on differently structured substrates. We found that even a pronounced asperity of the ground structure, with bumps of almost the size of the animal, was largely compensated by the walking apparatus of the blowfly, which leads to body roll and pitch movements only marginally larger than those on flat substrate. Pitch and roll fluctuations of the head were smaller compared with body fluctuations on all tested substrates, emphasizing the significance of gaze stabilization during walking on structured substrates. Furthermore, we found no impairment in head and body stabilization during walks in darkness, which indicates that the control system mediating compensatory head movements works well without any visual input. Interestingly, blowflies changed their walking style in the dark and seemed to use their forelegs as tactile probes.

Galvanic stimulation of the vestibular periphery in guinea pigs during passive whole body rotation and self-generated head movement

Irregular vestibular afferents exhibit significant phase leads with respect to angular velocity of the head in space. This characteristic and their connectivity with vestibulospinal neurons suggest a functionally important role for these afferents in producing the vestibulo-collic reflex (VCR). A goal of these experiments was to test this hypothesis with the use of weak galvanic stimulation of the vestibular periphery (GVS) to selectively activate or suppress irregular afferents during passive whole body rotation of guinea pigs that could freely move their heads. Both inhibitory and excitatory GVS had significant effects on compensatory head movements during sinusoidal and transient whole body rotations. Unexpectedly, GVS also strongly affected the vestibulo-ocular reflex (VOR) during passive whole body rotation. The effect of GVS on the VOR was comparable in light and darkness and whether the head was restrained or unrestrained. Significantly, there was no effect of GVS on compensatory eye and head movements during volitional head motion, a confirmation of our previous study that demonstrated the extravestibular nature of anticipatory eye movements that compensate for voluntary head movements.

Compensatory Head Movements in Blowflies Walking Freely on Differently Structured Substrates

Event Abstract Back to Event Compensatory Head Movements in Blowflies Walking Freely on Differently Structured Substrates Daniel Kress1, 2* and Martin Egelhaaf1, 2 1 Bielefeld University, Neurobiology, Germany 2 CITEC Center of Excellence Cognitive Interaction Technology, Germany Many insects such as flies and bees rely heavily on visual signals in order to obtain functionally relevant information about their environment. This is especially true for goal directed behaviors like the approach to an object of interest. The quality of these visual signals may deteriorate in walking animals as a consequence of the kinematic properties of the locomotor apparatus, which may lead to movements of the eyes contingent on the walking cycle. Moreover, locomotion on a rough terrain can cause huge unintended retinal image shifts. Consequently, various species evolved strategies to compensate for these unintended image shifts and, thus, to support visual information processing. An example are compensatory head movements, which stabilize the gaze and, thus, the orientation of the visual reference system by counterbalancing changes in body attitude during self-movement. Up to now, it is still unclear to what extent walking insects are able to stabilize their gaze when walking on structured ground. Furthermore, due to the complex multimodal control of head movements, it is unknown to what extent the visual system is involved in controlling potential stabilizing movements. To tackle these open questions, we analyzed by stereo high-speed video compensatory head movements of blowflies walking freely on differently structured substrate types. We found that even pronounced asperities of the ground structure with bumps of almost the size of the animal were largely compensated by the walking machinery of the blowfly. As a consequence, body roll and pitch movements are not much, but significantly larger than those on even ground. Pitch and roll fluctuations of the head were even smaller than those of the body on all tested substrates, emphasizing the significance of compensatory head/body coordination in flies when walking across difficult terrain. To assess the influence of the visual system on this compensatory performance, we filmed blowflies walking on different substrates in darkness (under unperceivable infrared illumination). Interestingly, blowflies changed their walking style in the dark and seemed to use their forelegs as tactile probes to get mechanosensory information. Nonetheless, head and body fluctuations were similar to those under normal light conditions, indicating that the control system mediating compensatory head movements during walking works fine without visual input. As the gaze of freely walking blowflies is apparently never completely rotationally stabilized even during walks on flat ground, we are currently analyzing how these residual fluctuations affect the spatial vision and fixation behavior during goal directed tasks in which the blowflies approach an attractive object. Figure 1 Keywords: Blowfly, Compensation, gaze, head movement, insect, stabilization, Vision, Walking Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster (but consider for student poster award) Topic: Sensory: Vision Citation: Kress D and Egelhaaf M (2012). Compensatory Head Movements in Blowflies Walking Freely on Differently Structured Substrates. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00079 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 30 Mar 2012; Published Online: 07 Jul 2012. * Correspondence: Mr. Daniel Kress, Bielefeld University, Neurobiology, Bielefeld, 33615, Germany, daniel.kress@uni-bielefeld.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract Supplemental Data The Authors in Frontiers Daniel Kress Martin Egelhaaf Google Daniel Kress Martin Egelhaaf Google Scholar Daniel Kress Martin Egelhaaf PubMed Daniel Kress Martin Egelhaaf Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.